Field devices for recording and/or modifying process variables are frequently used in process automation technology, as well as in manufacture automation technology. Measuring devices or sensors, such as level measuring devices, flow meters, pressure and temperature measuring devices, pH-redox potential meters, conductivity meters, etc., are used for recording the respective process variables such as fill-level, flow, pressure, temperature, pH level, and conductivity. Actuators, such as, for example, valves or pumps, are used to influence process variables. Thus, the flow rate of a fluid in a pipeline section or a fill-level in a container can be altered by means of actuators.
Field devices, in general, refer to all devices which are process-oriented and which provide or edit process-relevant information. In addition to the aforementioned measuring devices/sensors and actuators, units that are directly connected to a field bus and used for communication with superordinate units, such as remote I/O's, gateways, linking devices, and wireless adapters, are also generally referred to as field devices.
The company group Endress+Hauser produces and distributes a large variety of such field devices.
In modern industrial plants, field devices are usually connected with superordinate units via field bus systems, such as Profibus®, Foundation Fieldbus®, HART®, etc. Normally, the superordinate units are control systems or control units, such as an SPC (Stored Program Control) or a PLC (Programmable Logic Controller). The superordinate units are used, among other things, for process control, process visualization, and process monitoring, as well as commissioning of the field devices. The values recorded by field devices sensors, in particular are transmitted via the connected bus system to one, or possibly even multiple, superordinate unit(s). In addition to that, data transfer from the superordinate unit to the field devices via the bus system is required; in particular, it serves the purpose of configuration and parameterization of field devices, as well as diagnostics. In general terms, the field device is operated via the bus system from the superordinate unit.
In the context of the present disclosure, it is significant that a networking based upon the Internet Protocol (IP) is also increasingly being integrated into field devices in industrial environments. In addition to connection-oriented communication (for example, on the basis of what is known as the TCP protocol layer) and point-to-point message transfer, e.g., on the basis of what is known as the UDP protocol, data transfer of IP data packets via what are known as broadcast addresses and multicast addresses, in which data may be simultaneously relayed from a sending unit to multiple receivers, is supported as part of the Internet protocol family.
In addition to a wired data transfer between the field devices and the superordinate unit, e.g., Ethernet/IP, there is likewise a possibility for a wireless data transmission. In the bus systems Profibus®, Foundation Fieldbus® and HART® in particular, a wireless radio-based data transfer is specified. Moreover, radio networks for sensors are specified in the standard IEEE 802.15.4 in more detail. The IEEE standard describes only the two lower layers (PHY and MAC) in the ISO-OSI model for WPAN's (Wireless Personal Area Networks). The higher protocol layers are regulated by other organizations. This enables universal use of the IEEE 802.15.4 base layer. A multitude of different technologies are using this base layer and extend the protocol stack only on the higher layers. Thus, a basis for IP-based sensor networks was created by means of the IETF standard 6LoWPAN, for example.
To enable a wireless data transfer, current field devices have various radio interfaces such as WLAN, Bluetooth, and/or near-field communication (NFC). These interfaces can be used to establish a connection to the corresponding field device in order to enable access to its process data and/or field device data or parameters.
For this kind of data transfer, typically, operating devices preferably, mobile operating devices are used, which are also fitted with multiple radio interfaces. Such operating devices can, for example, be proprietary devices, as well as newer devices such as, for example, smartphones, notebooks, or iPad's. Depending upon the radio interface, different wireless standards and technologies using different protocols are used with these devices.
Depending upon the specification of the interface and the protocol used, the operators (a service technician, for example) need to be able to use these various connection and communication technologies in order to connect them. Especially when it comes to direct, on-site operations, various field devices with various interfaces have to be operated, one after another, within a very short period of time. This results in the operators needing to bring corresponding hardware and software along with them, having to have a great amount of knowhow about the differing, technology-specific usage of access interfaces specific to the technology, and having to spend a great deal of time on the different connection establishments.
To make things more complicated, with wireless connections, it is not obviously visually apparent to the operator which wireless protocol (e.g., WLAN, Bluetooth, 6LoWPan) is available for certain field devices. With wired connections such as Ethernet/IP, the user must know either the name of the corresponding field device, or, alternatively, its IP address, in order to establish a connection.
Both complicate the operation or pose possible sources of error, and mean a significant loss of time for the operator when it comes to practical usage of such field devices and operator devices.
Since a communication with a plurality of remote stations may be established based upon the Internet protocol, for the user, the difficulty exists of finding out which field devices he may contact via the IP network, or which IP addresses these devices have. In particular, it is not efficiently possible to probe all conceivable IP addresses via a scanning method. An IP network therefore differs significantly from other transmission methods, such as Bluetooth or ANT, in which there is, for example, the mechanism of what is known as “advertising,” in which the remote station periodically transmits broadcast messages, and it is thereby possible for the operator unit to easily establish which remote stations are currently within radio range.